This application claims priority of German Application No. 199 51 482.8, filed Oct. 26, 1999, the complete disclosure of which is hereby incorporated by reference.
a) Field of the Invention
The invention relates to the illumination of a specimen with laser light of different wavelengths, preferably in cross correlation variants of fluorescence correlation spectroscopy (FCS). However, it is also advantageously applicable in other microscope systems such as the laser scanning microscope and in the detection of time-resolved fluorescence in order to guide the illumination of a plurality of wavelengths simultaneously or sequentially to exactly the same location on the specimen.
b) Description of the Related Art
In cross correlation FCS, simultaneous spectrally separated detection of two differently marked reacting agents and their two-color reaction product is carried out. The mathematical comparison of the detector signals supplies information about the concentration and dynamics of the associated co-reactants without disruptive contributions from the individual components.
It is necessary to illuminate a small specimen volume which has a diameter in the range of the Airy disk with two lasers of different wavelength. The two volumes must overlap very well with one another.
Due to unavoidable manufacturing and alignment tolerances, a transverse chromatic aberration and therefore an insufficient overlapping of the volumes cannot be ruled out with illumination by different wavelengths.
It is the primary object of the invention to ensure the most exact possible overlapping of the volumes in the illumination with different wavelengths.
According to the invention, this object is met in an arrangement for illumination with a plurality of wavelengths in a microscope wherein correction optics are provided in a parallel beam path within the illumination/imaging optics for generating an exact overlapping of the wavelengths in the specimen volume in an adjustable manner.